Hello rajee46,
90K is not a small amount.
Did you check with the hospital if anyone from your company has been in touch with them? Obviously, the hospital will have to be contacted for any inquiry/investigation. That way, you will know 2 aspects of your situation:
1] Whether your HR is faking the reason or is the investigation genuine.
2] If genuine, you should be able to get the details of what this investigation is all about [depending on how you ask them].
Your next step will depend a lot on the inputs you gather from here.
Next, talk to the new company & buy more time--say a couple of weeks [maybe they may bargain for a week or so]--but you will have to SOUND CONVINCING with your reasons--you can tell them that your relieving has been delayed & you are pushing, WITHOUT telling them the actual reason. Pl note that this has to be handled tactfully, since there is every chance that the HR there COULD get a doubt that you are buying time to join elsewhere.
Next, talk to a lawyer to draft an Affidavit, explaining the reason why you want it. Whether you finally use it or not is not the issue. If you have it ready in-hand, you will not loose any further time. And also, depending on what info you gather from the hospital, you could discuss the next course of action too [especially if the 'so called investigation' turns out to be false].
And, needless to mention, the members of CiteHR are always available to give their best possible well-meant suggestions.
AND ALSO, FOR NOW, pl desist from discussing anything with your HR or others in your present company--just 'let it be'. Once they notice your silence, someone from HR is sure to ask you 'why'--just laugh it off & hold all your cards close to your chest. Until you have all the inputs in-hand.
All the Best.
Rgds,
TS